Recently, a small-sized and lightweight image projection apparatus has been developed. This type of image projection apparatus is configured not to include a heavy Philips prism as disclosed for example in U.S. Pat. No. 7,144,116 (PTD 1), and includes total reflection prisms, digital mirror devices, and a color synthesis prism, for example. Light is split into a plurality of color lights which are reflected by the total reflection prisms to be incident on the digital mirror devices. The lights reflected by the digital mirror devices toward the color synthesis prism are synthesized by the color synthesis prism to thereby form an image.
The image projection apparatus is required to project an image with high precision. Japanese Laid-Open Patent Publication No. 10-319524 (PTD 2) for example is a document disclosing an image projection apparatus which is different in structure from the image projection apparatus disclosed in PTD 1, but with which registration deviation can be prevented and an excellent image can be obtained.
The image projection apparatus disclosed in PTD 2 includes polarization beam splitters, light valves, and a color synthesis prism. Light entering the polarization beam splitter is polarized and separated, and only the S-polarized light of the polarized and separated light is incident on the light valve. The light reflected from the light valve passes through the polarization beam splitter, enters the color synthesis prism, and is synthesized by the color synthesis prism.
The light valve is fixed to the polarization beam splitter so that the load of the light valve is exerted on the polarization beam splitter. With the registration adjusted, the light valve and the polarization beam splitter are integrated together to thereby enable prevention of registration deviation.